Methods and systems for forming microstructures in glass substrates

ABSTRACT

A method for forming microstructure cavities in a glass substrate includes directing a first laser pulse onto the glass substrate thereby forming a first microstructure cavity having a tapered configuration. The first laser pulse may have first spot area on the surface of the glass substrate. A second laser pulse having a second spot area on the surface of the glass substrate may be directed onto the glass substrate thereby forming a second microstructure cavity having a tapered configuration. The second spot area may be substantially the same as the first spot area and may overlap the first spot area such that a portion of the sidewall disposed between first microstructure cavity and the second microstructure cavity is ablated. After the portion of the sidewall is ablated, the diameter of each of the first and second microstructure cavities may be less than the diameter of the first spot area.

TECHNICAL FIELD

The present invention generally relates to systems and methods forforming structures in glass substrates and, more specifically, to lasersystems and methods for using laser systems to form microstructures inglass substrates through laser ablation.

BACKGROUND

Glasses, such as high content silica glass and boro-silicate glass, havemany properties of interest for chemical, pharmaceutical, optical andbiological applications including chemical inertness, high temperaturedurability, optical transparency, controllable surface wettingproperties and the like. Positive topographical features (e.g., pillars,columns, grids and the like) and negative topographical features (e.g.,cavities, voids, grooves and the like) may be introduced into a glasssubstrate to make the glass substrate suitable for a particularapplication. Conventional machining and molding techniques are commonlyused to introduce features on the order of 1 mm and greater into a glasssubstrate while photolithography and chemical etching are commonly usedto introduce features smaller than 1 mm (i.e., microstructures) into aglass substrate. These glass microstructures have potential forapplication in, for example, micro-fluidics, hyperhydrophobic surfaces,micro-cavity arrays, micro-lens systems, life science cells,micro-reactor mixing designs.

However, the photolithography and chemical etching techniques used forproducing microstructures in glass are difficult to apply compared tothe more conventional machining and molding techniques. Further,processes such as photolithography may be expensive and time consumingand therefore are not economically viable for small manufacturing runsand rapid prototyping.

Accordingly, alternative methods for producing microstructures in glassthat are suitable for small manufacturing runs and prototyping.

BRIEF SUMMARY OF THE INVENTION

According to one embodiment, a method for forming microstructures in aglass substrate by laser ablation may include directing a beam of alaser source onto a surface of the glass substrate and traversing thebeam across the surface of the glass substrate such that a spot area ofthe beam forms a first pattern on the surface of the glass substrate andglass is ablated from the glass substrate along the first pattern. Themethod may also include directing a beam of a laser source onto asurface of the glass substrate and traversing the beam across the glasssubstrate such that the spot area of the beam forms at least one secondpattern on the surface of the glass substrate. The second or subsequentpattern may overlap or intersect with the first pattern. Glass may beablated from the surface of the glass substrate along the second orsubsequent pattern thereby forming at least one microstructure on theglass substrate.

According to another embodiment, a method for forming microstructurecavities in a glass substrate includes directing a first laser pulseonto the glass substrate thereby forming a first microstructure cavityhaving a tapered configuration in the glass substrate. The first laserpulse may have first spot area where the laser pulse intersects with thesurface of the glass substrate. A second laser pulse having a secondspot area where the laser pulse intersects with the surface of the glasssubstrate may be directed onto the glass substrate thereby forming asecond microstructure cavity having a tapered configuration in the glasssubstrate. The second spot area may be substantially the same as thefirst spot area. The second spot area may also overlap the first spotarea such that a portion of the sidewall disposed between firstmicrostructure cavity and the second microstructure cavity is ablated.After the portion of the sidewall is ablated, the diameter of the firstmicrostructure cavity and the diameter of the second microstructurecavity may be less than the diameter of the first spot area, the secondspot area or both.

Additional features and advantages of the invention will be set forth inthe detailed description which follows and, in part, will be readilyapparent to those skilled in the art from that description or recognizedby practicing the invention as described herein, including the detaileddescription which follows, the claims, as well as the appended drawings.It is to be understood that both the foregoing general description andthe following detailed description present embodiments of the inventionand are intended to provide an overview or framework for understandingthe nature and character of the invention as it is claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of specific embodiments of thepresent invention can be understood when read in conjunction with thefollowing drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 is a block diagram generally showing the component of a laserablation system used to form microstructures in glass substratesaccording to one embodiment shown and described herein;

FIG. 2 depicts a cross section of a glass substrate having a taperedmicrostructure cavity formed by laser pulse incident on the surface ofthe glass substrate;

FIG. 3 depicts a top view of a glass substrate showing a first spot areaof an first beam pulse incident on the surface of the glass substrateoverlapped by a second spot area of a second beam pulse incident on thesurface of the glass substrate according to one embodiment shown anddescribed herein;

FIG. 4 depicts a cross section of the glass substrate shown in FIG. 3showing a first microstructure cavity and a second microstructure cavityformed according to one method for forming microstructures in glasssubstrates shown and described herein;

FIG. 5 depicts a pattern of spot areas from a plurality of beam pulsesincident on the surface of a glass substrate for forming a honeycombpattern of microstructure cavities according to one method for formingmicrostructures in glass substrates shown and described herein;

FIG. 6 depicts a cross section of the glass substrate of FIG. 5 having aplurality of microstructure cavities formed according to one method forforming microstructures in glass substrates shown and described herein;

FIG. 7 shows a top view of a glass substrate having a honeycomb patternof microstructure cavities formed according to one method for formingmicrostructures in glass substrates shown and described herein;

FIG. 8 depicts a pattern of sets of parallel lines scribed into thesurface of a glass substrate to form square microstructure pillarsaccording to one method for forming microstructures in glass substratesshown and described herein;

FIG. 9 shows a top view of a glass substrate having a regular pattern ofsquare microstructure pillars formed according to one method for formingmicrostructures in glass substrates shown and described herein;

FIG. 10 shows a top view of a glass substrate having a regular patternof triangular microstructure pillars formed according to one method forforming microstructures in glass substrates shown and described herein;

FIG. 11A depicts a first pattern of spot areas of laser pulses incidenton the surface of a glass substrate to form a circular microstructurepillar according to one method for forming microstructures in glasssubstrates shown and described herein;

FIG. 11B depicts at least one second pattern of spot areas of laserpulses incident on the surface of a glass substrate to form a circularmicrostructure pillar according to one method for formingmicrostructures in glass substrates shown and described herein; and

FIG. 12 shows a top view of a glass substrate having a regular patternof circular microstructure pillars formed according to one method forforming microstructures in glass substrates shown and described herein.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

Referring initially to FIG. 1, a laser system for formingmicrostructures in glass substrates is shown. The system may generallycomprise a laser source, a beam steering mechanism for directing andscanning laser pulses of the laser source onto a glass substrate, a lenssystem for focusing the beam onto the glass substrate and a work tableon which the glass substrate may be positioned. Each of the elements ofthe system as well as various methods for using the systems to formmicrostructures in a glass substrate will be discussed in more detailherein.

Referring now to FIG. 1, a laser system 100 for directing, focusing andscanning a beam 112 from a laser source 102 onto a glass substrate 108is shown. The laser system 100 may generally comprise a laser source102, a beam steering mechanism 104, and a lens system 106. In oneembodiment, the laser system 100 may also comprise a multi-axis worktable 110 on which a work piece (e.g., the glass substrate 108) may bepositioned.

The laser source 102 may generally comprise a laser source having anoutput power sufficient to ablate glass from the surface of the glasssubstrate. As such, the laser source may generally comprise a Nd:YAGlaser, a Nd:YVO₄ laser, a ND:YLF laser, a CO₂ laser or the like. In oneembodiment, the laser source 102 may generally be capable of beingoperated in a pulsed output mode such that the beam 112 of the lasersource comprises discrete laser pulses. Preferably, the laser is pulsedbelow the rise time of the laser, to result in a short pulse time (e.g.less than 100 microseconds, more preferably less than 80 microseconds).In one particular embodiment, the laser source may comprise a CO₂ laseroperated in a manner to produce a beam comprising a plurality ofdiscrete laser pulses. For example, a typical pulse rise time for a CO₂laser is on the order of 100 μs and, after the pulse reaches full power,the CO₂ laser is generally operated as a continuous wave output laser.However, by switching the laser off during the pulse rise time, the CO₂laser may be operated in a pulsed mode. Accordingly, in one embodiment,the CO₂ laser is operated in pulsed mode by switching the laser on andswitching the laser off during the pulse rise time such that laserpulses on the order of about 55 μs to about 80 μs are produced with eachlaser pulse having an energy of about 15 μJ to about 100 μJ, morepreferably 20 μJ to about 80 μJ and most preferably about 25 μJ to about40 μJ at the output of the laser source. The duration of each pulse maybe varied to control the amount of material removed from the surface ofthe glass substrate by ablation. The beam 112 may generally have adiameter d_(B) of approximately 2 mm at the output of the laser source102.

In another embodiment the laser source 102 may generally be capable ofbeing operated in a continuous wave output mode such that the beam 112of the laser source comprises a continuous beam. For example, in oneembodiment, the laser source may comprise a CO₂ laser operated incontinuous wave mode. The output of the CO₂ laser may be regulated bypulse width modulation (PWM) to produce an average power output that isessentially continuous. Typical modulation frequencies to produce thecontinuous wave output of the CO₂ laser system are preferably from about1 kHz to about 20 kHz with a period of about 1 ms to about 50 μs.Standard modulation frequencies for continuous wave operation are mostpreferably about 5 kHz with a period of about 200 μs.

Accordingly, it should now be understood that the methods and systemsdescribed herein may utilize a laser source operated in continuous wavemode or pulsed mode to form microstructures in the surface of the glasssubstrate.

The beam 112 of the laser source 102 is directed into the beam steeringmechanism 104 where the beam 112 is redirected towards the glasssubstrate 108. The beam steering mechanism 104 may generally comprise atleast one scanning mirror (not shown), such as a fast scanning mirror,which is used to redirect the beam 112 onto the surface of the glasssubstrate 108. In one embodiment, the beam steering mechanism 104 maycomprise a pair of galvanometer mirrors. Each galvanometer mirror may bepositioned to rotate about a different axis such that the beam may bescanned across the surface of the glass substrate 108 along 2 axes.

After the beam 112 is redirected by the beam steering mechanism 104, thebeam 112 may pass through a lens system 106 which focuses the beam ontothe surface of the glass substrate. For example, when the laser sourceis a CO₂ laser with an output beam diameter d_(B) of 2 mm, the lenssystem 106 may be used to focus the beam such that the beam spot of thelaser pulse 112 has a diameter d_(SA) of 55 μm on the surface of theglass substrate. In another embodiment, the lens system 106 may comprisean F-theta lens as is commonly known in beam scanning applications. TheF-theta lens may facilitate focusing the 2 mm diameter beam down to the55 μm diameter spot area while also providing a flat field at the imageplane (e.g., the surface 109 of the glass substrate 108) of the scan. Inother words, for a specified working area, the beam output of theF-theta lens is substantially perpendicular to the surface of the glasssubstrate 108 for any position on the surface of the glass substratewithin the working area. For example, in one embodiment, the F-thetalens may produce a 55 μm diameter spot area over a 25 mm×25 mm workingarea wherein the output of the F-theta lens is substantiallyperpendicular to the surface of the glass substrate.

The laser system 100 may also comprise a multi-axis work table 110. Themulti-axis work table 110 may be used to position the glass substrate108 during the laser ablation process. The multi-axis work table 110 mayalso be used to position the glass substrate 108 relative to the lenssystem 106 in the x-y plane and z directions. In one embodiment, whenthe lens system 106 comprises an F-theta lens with a reduced workingarea, the multi-axis work table 110 may be used to position the glasssubstrate relative to the F-theta lens effectively increasing theworking area of the F-theta lens.

Accordingly, the beam steering mechanism 104 in combination with thelens system 106 may be used to focus and position beam 112 from thelaser source 102 onto the surface of the glass substrate 108 at discretepositions. Moreover, because the output of the laser source 102 is ofsufficient power to ablate glass from the surface of the glass substrate108, the laser system 100 may be used to ablate glass from the glasssubstrate 108 thereby facilitating the introduction of various patternsin the surface of the glass substrate 108 via laser ablation therebyforming glass microstructures in the surface of the glass substrate 108.

Referring now to FIGS. 2-7, one embodiment of a method for formingmicrostructures in a glass substrate by laser ablation is shown. In thisembodiment a laser system, such as the laser system 100 depicted in FIG.1, may be used to direct a beam from the laser source onto the surfaceof a glass substrate such that the spot area of the beam forms a patternon the surface of the glass substrate. The beam may be pulsed and thespot areas of each laser pulse in the pattern may overlap a spot area ofa proceeding laser pulse, a spot area of a subsequent laser pulse orboth thereby forming a plurality of microstructure cavities in ahoneycomb pattern in the surface of the glass substrate. Using themethod described herein, each microstructure cavity in the honeycombpattern has a diameter smaller than the diameter of a spot area of thebeam on the surface of the glass substrate.

To form a microstructure cavity 118 in the surface 109 of the glasssubstrate 108 using a laser source operated in a pulsed mode, a firstlaser pulse may be directed onto the surface 109 of the glass substrate108. The first laser pulse may be focused onto the surface 109 such thatthe first laser pulse has a first spot area 116 of diameter d_(SA) onthe surface 109 of the glass substrate. The diameter of the spot area116 at the surface 109 of the glass substrate may be substantiallysmaller than the diameter d_(B) of the laser pulse at output of thelaser source 102 such that the laser pulse incident on the surface 109of the glass substrate has sufficient energy density to exceed theablation threshold for the glass substrate thereby ablating a firstmicrostructure cavity 118 into the surface 109 of the glass substrate108. This first microstructure cavity may have an initial diameter atthe surface 109 of the glass substrate 108 substantially the same as thediameter d_(SA) of the spot area 116 of the first laser pulse on thesurface of the glass substrate 108. The first microstructure cavity 118has sidewalls 121, 123 which as seen in FIG. 2 taper to a decreasinginternal diameter with increasing depth below the surface 109 of theglass substrate 108 due to attenuation of the energy of the laser pulseduring ablation.

A second laser pulse having a second spot area 120 is directed towardsand focused onto the surface 109 of the glass substrate 108. The spotarea 120 of the second laser pulse has a diameter d_(SA) such that thespot area 120 of the second laser pulse is substantially the same as thespot area 116 of the first laser pulse. Using the beam steeringmechanism 104 of the laser system 100 shown in FIG. 1, the second laserpulse may be directed onto the surface 109 of the glass substrate 108such that the spot area 120 of the second laser pulse overlaps the spotarea 116 of the first laser pulse thereby ablating a secondmicrostructure cavity 124 having a tapered configuration into thesurface 109 of the glass substrate 108. Because the spot area 120 of thesecond laser pulse overlaps the spot area 116 of the first laser pulse,a portion of the sidewall 127 between the first microstructure cavityand the second microstructure cavity is abated along with acorresponding portion of the surface 109 of the glass substrate. Afterthe portion of the sidewall 127 is ablated, the diameter d_(MS) of theopening in the first microstructure cavity is the same as the diameterd_(MS) of the opening in the second microstructure cavity, both of whichare less than the diameter d_(SA) of the spot area of the first laserpulse or the second laser pulse on the surface 109 of the glasssubstrate. It should be understood that the diameter of the opening of amicrostructure cavity refers to the diameter of the widest portion ofthe microstructure cavity. Because both the first and secondmicrostructure cavities have a tapered configuration, the ablation of aportion of the sidewall 127 and a corresponding portion of the surfacebetween the microstructure cavities results in microstructure cavitieswith opening diameters d_(MS) which are less than the diameter d_(SA) ofthe spot area incident on the original surface of the glass substrate.Accordingly, by overlapping the spot areas of adjacent laser pulses,microstructure cavities may be formed in the glass substrate via laserablation such that the diameter of the opening of the microstructurecavity is smaller than the diameter of the laser pulse used to ablatethe glass and form the microstructure cavity. For example, if the spotareas of the laser pulses are 55 μm on the surface of the glasssubstrate, the resulting microstructure cavities formed due to theoverlap of spot areas will generally have an opening diameter d_(MS) ofless than about 50 μm, more preferably less than about 40 μm and mostpreferably less than about 30 μm. Accordingly, for a given diameterd_(SA) of a spot area on the surface of the glass substrate, theresulting microstructure cavities will have an opening diameter of lessthan about the opening diameter of each microstructure cavity is lessthan about 0.90*d_(SA), more preferably less than about 0.7*d_(SA), andmost preferably less than about 0.55*d_(SA).

While reference is made herein to directing a first laser pulse and asecond laser pulse against the surface of the glass substrate 108 itshould be understood that the first laser pulse and the second laserpulse may be directed towards the surface of the glass simultaneously,such as when multiple laser systems 100 are used to redirect a pluralityof beam spots against the surface of the glass substrate 108.

Referring to FIG. 3, the opening diameters d_(MS) of the first andsecond microstructure cavities may be controlled by adjusting thespacing between adjacent laser pulses and, therefore, the overlap 122between adjacent spot areas. Accordingly, by increasing the overlap (ordecreasing the spacing between spot areas of consecutive laser pulses),more of the sidewall between adjacent microstructures cavities isremoved. Because the sidewalls between the cavities are tapered,removing more of the sidewall (or decreasing the height of the sidewall)reduces the diameter of the opening of the microstructure cavity.Accordingly, the opening diameter of the resulting microstructurecavities may be adjusted by adjusting the spacing between consecutiveadjacent laser pulses such that adjacent spot areas overlap.

The technique of overlapping the spot areas of laser pulses to createmicrostructure cavities in the surface of a glass substrate may berepeated multiple times to form a pattern of microstructure cavities inthe surface 109 of a glass substrate 108 as shown in FIGS. 5-8. In oneembodiment, a plurality of laser pulses may be directed and focused onto the surface 109 of the glass substrate 108 such that a spot area ofeach laser pulse overlaps a spot area of a preceding laser pulse, a spotarea of a subsequent laser pulse or both. For example, as shown in FIGS.5 and 6, a first plurality of laser pulses may be directed onto thesurface 109 of the glass substrate 108 along a line such that the spotareas of the laser pulses form a first linear pattern 128 of overlappingspot areas 126 with each spot area 126 representing the formation of amicrostructure cavity 125 in the glass substrate via laser ablation.

Thereafter, a second or subsequent plurality of laser pulses may bedirected onto the surface 109 of the glass substrate 108 along a linesuch that the spot areas of the laser pulses form a second or subsequentlinear pattern 130 of overlapping spot areas 126 with each spot area 126representing the formation of another microstructure cavity 125 in theglass substrate through laser ablation. The second or subsequent linearpattern 130 may be generally parallel to the first linear pattern 128and may generally overlap the first linear pattern 128 such that eachspot area 126 overlaps every adjacent spot area 126 such that themicrostructure cavities formed generally have diameters and pitch(distance between center point of the microstructure cavities) smallerthan the diameters of the spot areas in the first linear pattern and thesecond or subsequent linear pattern 130. For example, for a 50 micronbeam spot size, structures can be made whose center points are 20microns apart. Thus, for example, structures can be achieved whose pitch(distance between centers) is less than the spot size of the laser, morepreferably less than 0.75 times the spot size of the laser, and in someinstances can be even less than 0.5 times the spot size of the laser.Further, the second or subsequent linear pattern 130 may be linearlyoffset from the first linear pattern 128 such that the center of eachspot area 126 in the first linear pattern 128 may be disposed betweenthe centers of two adjacent spot areas 126 in the second or subsequentlinear pattern 130. More particularly, the first linear pattern 128 maybe linearly offset from the second or subsequent linear pattern 130 suchthat the center points of any three mutually adjacent spot areas 126(e.g., spot areas 126A, 126B, and 126C) form the vertices of anisosceles or equilateral triangle 134. Additional second or subsequentlinear patterns 132 of overlapping spot areas 126 may be used thereafterto form a honeycomb pattern of microstructure cavities 125 in thesurface 109 of the glass substrate 108 as shown in FIG. 7.

It should now be understood that microstructures, specificallymicrostructure cavities, may be formed in the glass substrate throughlaser ablation by directing a plurality of laser pulses onto the surfaceof a glass substrate such that the spot areas of the laser pulses forman overlapping pattern of spot areas and, because the spot areas of thelaser pulses overlap, the opening diameters of the resultingmicrostructure cavities may be less than the diameter of the spot areasused to form the microstructure cavities.

Referring now to FIGS. 8 and 9, another embodiment of a method forforming microstructures in a glass substrate by laser ablation is shown.In this embodiment, a laser system as depicted in FIG. 1 may be used todirect a beam onto the surface of the glass substrate along sets ofparallel lines. The parallel lines are scribed into the glass substrateby using the laser system 100 to ablate glass along parallel lines.Therefore, by using the laser system 100 to scribe multiple sets ofparallel lines having different relative orientations, a pattern ofmicrostructures 156 may be formed in the glass substrate at theinterstices between the intersections of different sets of parallellines.

As shown in FIG. 8, in one embodiment, a first set of parallel lines 152is scribed into the surface of the glass substrate by directing aplurality of laser pulses from a laser source operated in pulsed modealong multiple parallel lines 151 such that each line in the first setof parallel lines comprises a row of overlapping spot areas 162 andthereby ablating glass from the glass substrate along the parallel lines151. The pitch P_(r) of the parallel lines 151 may be selected andadjusted according to the desired dimensions of the resultantmicrostructures. The laser pulses (not shown) are centered on theparallel lines 151 such that each pulse of the plurality of laser pulseshas as spot area 164 on the surface of the glass substrate that iscentered on a parallel line 151. The spot area 164 of each laser pulsealong a parallel line 151 may overlap a spot area of a preceding laserpulse, a spot area of a subsequent laser pulse or both such that a rowof overlapping spot areas 162 may be defined by substantially paralleledges 163 tangential to each spot area 164 on either side of the row ofoverlapping spot areas 162. To reach this result, each spot area 164 mayoverlap a spot area of a preceding laser pulse, the spot area of asubsequent laser pulse or both by greater than about fifty percent ofthe diameter of a spot area.

After the first set of parallel lines 152 is scribed into the surface ofthe glass substrate, a second or subsequent set of parallel lines 154may be scribed into the surface of the glass substrate in the samemanner as the first set of parallel lines 152. In the embodiment shownin FIG. 8 the second or subsequent set of parallel lines 154 is scribedinto the glass substrate by using the laser system to direct laserpulses along parallel lines 161 thereby scribing the second set ofparallel lines 154 into the surface of the glass substrate. As shown inFIG. 8, the parallel lines 161 are oriented perpendicular to theparallel lines 151. Accordingly, the second set of parallel lines 154scribed into the surface of the glass substrate are perpendicular to thefirst set of parallel lines 152. This results in the formation of aregular, repeating pattern of microstructure pillars 156 having squareor rectangular cross sections at the interstices between theintersections of the first set of parallel lines 152 and the second setof parallel lines 154 as shown in both FIGS. 8 and 9. The pillar canhave a top surface or height equal to the upper surface 109 of the glasssubstrate 108, or alternatively can be “submerged” below the surface109.

As indicated herein above, the pitch P_(r) of the parallel lines 151 andthe pitch P_(r) of the parallel lines 161 may be selected and adjustedto control the size and shape of the resulting microstructure pillars156. For example, to produce square microstructure pillars, the pitchP_(r) of the parallel lines 151 and the pitch P_(r) of the parallellines 161 may be selected to be the same. To produce rectangularmicrostructure pillars, the pitch P_(r) of the parallel lines 151 andthe pitch P_(r) of the parallel lines 161 may be selected to bedifferent. Further, the size of the resulting microstructures pillars156 can be adjusted by increasing or decreasing the pitch of theparallel lines 151, 161. In one embodiment, the pitch of the parallellines 151, 161 are selected such that the resulting microstructurepillars 156 have edge dimensions (e.g. length and width) smaller thanthe diameter of the spot area of the laser pulses used to form themicrostructure pillars. For example, for a spot area of 55 μm, the pitchof the lines 151, 161 may be selected to be 75 μm such that theresulting microstructure pillars are 20 μm×20 μm square microstructurepillars. Accordingly, for a spot area having a diameter d_(SA) on thesurface of the glass substrate, the pitch of the lines 151, 161 may beselected such that an edge dimension of the microstructure pillar areless than about 0.75*d_(SA), more preferably less than about 0.5*d_(SA),and most preferably less than about 0.40*d_(SA).

While FIGS. 8 and 9 shows ablating glass from a glass substrate alongtwo sets of parallel lines having a 90 degree orientation with respectto one another to form square or rectangular microstructure pillars, itshould now be understood that microstructure pillars having differentshapes may be formed by ablating glass from a glass substrate along twoor more sets of parallel lines with the sets of parallel lines havingnon-parallel orientations with respect to one another. For example, inone embodiment, diamond-shaped microstructure pillars may be formed atthe interstices between intersections of two sets of parallel lines,each set of parallel lines having a 45 degree orientation with respectto the other set of parallel lines. In another embodiment, as shown inFIG. 10, triangular microstructure pillars may be formed at theinterstices between intersections of three sets of parallel linesoriented at 60 degrees to one another. Accordingly, various shapes andpatterns of microstructure pillars may be formed using various patternsof intersecting sets of parallel lines scribed into the surface of theglass substrate using the laser ablation techniques described herein.

Moreover, while specific reference has been made herein to scribing thefirst and second sets of parallel lines 152, 154 into the glasssubstrate by directing a plurality of laser pulses from a pulsed beamalong parallel lines 151, 161, it should be understood that the firstand second sets of parallel lines 152, 154 may also be scribed into theglass substrate by using the laser source 102 of the laser system 100 ina continuous wave output mode such that the output beam is continuous.For example, the first and second set of parallel lines 152, 154 may bescribed into the glass substrate by directing a continuous beam of thelaser source onto the glass substrate and traversing the beam over thesurface of the glass substrate along the parallel lines 151, 161 therebyablating glass along the parallel lines 151, 161 and scribing the firstand second sets of parallel lines into the glass substrate. The rows ofoverlapping spot areas shown in FIG. 8 generally indicate the pathwaysalong which the continuous beam was traversed. The result is theformation of square or rectangular microstructure pillars at theinterstices between the intersections of the first and second sets ofparallel lines 152, 154. The edge dimensions (i.e., the length of theedges) of the resulting microstructure pillars may be controlled byadjusting the pitch P_(r) of the parallel lines 151, 161.

Referring now to FIGS. 11A-12, another embodiment of a method forforming microstructures in a glass substrate is shown in which a beamfrom a laser source comprising a plurality of laser pulses is directedonto the surface of a glass substrate in radial patterns to ablate glassfrom the glass substrate at discrete positions along the radial patternand thereby produce a circular microstructure pillar 178. Using thesystem depicted in FIG. 1 to control the position of laser pulsesincident on the glass substrate, a first plurality of consecutive laserpulses are directed onto the surface of the glass substrate in acircular pattern such that the spot areas 172 of each laser pulse form afirst radial pattern 170 having a radius R on the surface of the glasssubstrate. Each laser pulse is directed onto the surface of the glasssubstrate such that the center of each spot area 172 of each laser pulseis equidistant from the center point 174. Accordingly, the center ofeach spot area 172 lies along a circle of radius R centered on thecenter point 174. Further, the spot area of each laser pulse 172overlaps a spot area of a preceding laser pulse, a spot area of asubsequent laser pulse or both. The size of the resulting microstructure175 may be increased or decreased by increasing or decreasing the radiusR of the first radial pattern and/or by decreasing the spacing betweenadjacent laser pulses (e.g., increasing the overlap between adjacentspot areas) and adding additional laser pulses to the first radialpattern 170.

As shown in FIG. 11A, the microstructure 175 remaining at the center ofthe first radial pattern 170 after glass is ablated from the glasssubstrate has an irregular, star-shaped configuration in cross section.To refine the microstructure 175 into a microstructure pillar having acircular cross section a second or subsequent plurality of laser pulsesmay be applied to the glass substrate in a second or subsequent radialpattern 176, such as that shown in FIG. 11B, thereby ablating glass fromthe glass substrate at discrete positions along the second or subsequentradial pattern 176. The second or subsequent radial pattern 176 may becentered about the same center point 174. In one embodiment, the centerof each spot area 173 of each laser pulse in the second or subsequentradial pattern 176 may generally lay on the same circle of radius R suchthat each spot area 173 is equidistant from the center point 174, aswith the first radial pattern 170. In another embodiment, the center ofeach spot area 173 of each laser pulse in the second or subsequentradial pattern 176 may lay on a circle having a radius less than theradius R of the first radial pattern. In either embodiment, the secondor subsequent radial pattern 176 may be rotationally offset from firstradial pattern such that portions of the glass substrate not ablated bythe first plurality of laser pulses in the first radial pattern 170 areablated by the second or subsequent plurality of laser pulses in thesecond or subsequent radial pattern 176 thereby refining the shape ofthe star-shaped microstructure 175 into a circular microstructure pillar178 as shown in FIG. 11B. As with the first radial pattern 170, the spotarea 173 of each laser pulse in the second or subsequent radial pattern176 may overlap a spot area of a preceding laser pulse, a spot area of asubsequent laser pulse or both.

It should now be understood that a plurality of radial patterns of laserpulse spot areas may be applied to the glass substrate to refine theshape of the circular microstructure pillar 178. Moreover, it should beunderstood that, by using the method of applying multiple radialpatterns of laser pulse spot areas, circular microstructure pillars ofvarious cross sectional sizes may be created on the surface of the glasssubstrate. These methods may be repeated over the surface of the glasssubstrate such that a regular pattern of circular microstructure pillarsmay be created over the surface of the glass substrate as shown in FIG.12. Further, using these methods, circular microstructure pillars may becreated having cross sectional dimensions smaller than the diameter ofthe spot area of the laser pulse used to create the microstructure.Further, the size of the cross section of the circular microstructurepillar may be varied by adjusting the radius of the radial pattern, thenumber of pulses in the radial pattern, the overlap of adjacent pulsesin the radial pattern or various combinations thereof. In oneembodiment, for a spot area having a diameter d_(SA) on the surface ofthe glass substrate, the radius R of the first and second radialpatterns may be selected such that the resulting circular microstructurepillar has a diameter of less than about 0.90*d_(SA), more preferablyless than about 0.75*d_(SA), and most preferably less than about0.50*d_(SA).

Further, using the method of applying multiple radial patterns of laserpulse spot areas, circular microstructure pillars may be formed havingcross sectional dimensions larger than the diameter of the spot area ofthe laser pulse used to create the microstructure. This may beaccomplished by selecting the radius R of the first and second patternsto be larger than the diameter d_(SA) of the spot area of each beampulse incident on the surface of the glass substrate.

It should also be understood that additional radial patterns of laserpulses may be applied to the surface of the glass substrate to alter thephysical characteristics of the circular microstructure pillar, such asthe surface wetting properties and the like, through ablation. Further,it should also be understood that the process of ablating glass along aradial pattern on the surface of a glass substrate may be repeatedmultiple times around different center points to create a regularpattern of circular glass microstructures 178 as shown in FIG. 12.Moreover, as shown in FIG. 12, an additional laser pulse may be directedonto the glass substrate at the center point 175 to create a cavity 180at the center of each circular microstructure pillar 178.

In another embodiment, the radius R of the first radial pattern 170 maybe selected such that the spot areas 172 of each laser pulse intersector overlap at the center point 175. For example, in one embodiment, theradius R of the first radial pattern 170 may be less than the radius ofeach spot area in the first radial pattern. In this embodiment, amicrostructure cavity centered on the center point 174 is formed insteadof a circular microstructure pillar as glass at the center of the firstradial pattern 170 is ablated from the surface of the glass substrate.The microstructure cavity will generally have a diameter greater thanthe diameter of the spot areas used to create the microstructure cavity.A second or subsequent radial pattern of overlapping spot areas centeredon the center point 174 and rotationally offset from the first radialpattern may then be used to further refine the shape of the circularmicrostructure cavity.

Moreover, while specific reference has been made herein to directinglaser pulses onto the glass substrate in first and second radialpatterns 170, 176 to create a circular microstructure pillar or cavityin the glass substrate, it should be understood that circular glassmicrostructures may also be formed by using a continuous wave output ofa laser source. For example, a continuous beam from a laser source maybe directed onto the glass substrate using a laser system such as shownin FIG. 1. The continuous beam may be directed onto the surface of theglass substrate and traversed over the substrate in a radial patternhaving a radius R thereby creating a glass microstructure at the centerof the radial pattern. The overlapping spot areas 172 shown in FIG. 11Agenerally show the path along which the continuous beam may betraversed. Depending on the selected radius of the radial pattern, theglass microstructure may be a circular microstructure pillar or circularmicrostructure cavity. The continuous wave output of the laser sourcemay be directed onto the surface in a second or subsequent radialpattern overlapping the first pattern to refine the shape and dimensionsof the microstructure as discussed hereinabove.

It should now be understood that the system and methods shown anddescribed herein may be used to form microstructures and, morespecifically, patterns of microstructures on glass substrates. Whilespecific examples shown and described herein have made reference to theuse of the methods and systems of the present invention in conjunctionwith flat glass substrates, it should be understood that the systems andmethods may be used to form microstructures on glass substrates havingvarious other configurations such as glass rods, tubes, curved surfacesand the like. Moreover, is should now also be understood that thesystems and methods described herein provide a faster and more costeffective alternative to photolithography and chemical etching forforming microstructures in glass substrates as no masking or applicationof other/additional chemicals is necessary.

Further, it should now be apparent that the microstructures formed inglass substrates using the systems and methods described herein may havepotential for application in micro-fluidics, hyperhydrophobic surfaces,micro-cavity arrays, micro-lens systems, life science cells,micro-reactor mixing designs and the like. For example, the systems andmethods described herein may be used to produce glass substrates withmicrostructures for use in conjunction with, for example, micro-fluidicssystems, hyperhydrophobic surfaces, micro-cavity arrays, micro-lenssystems, life science cells, and micro-reactor mixing designs.Accordingly, glass substrates made with or according to the systems andmethods described herein may be used in biological applications,chemical applications, pharmaceutical applications, optical applicationsand the like.

It will be apparent to those skilled in the art that variousmodifications and variations may be made to the present inventionwithout departing from the spirit and scope of the invention. Thus it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and the

1. A method of forming microstructures on a glass substrate by laserablation, the method comprising: directing a beam of a laser source ontoa surface of the glass substrate and traversing the beam across thesurface of the glass substrate such that a spot area of the beam forms afirst pattern on the surface of the glass substrate as the beam istraversed across the glass substrate and glass is ablated from the glasssubstrate along the first pattern; and directing the beam of the lasersource onto the surface of the glass substrate and traversing the beamacross the surface of the glass substrate such that the spot area of thebeam forms a second or subsequent pattern on the surface of the glasssubstrate as the beam traverses across the glass substrate wherein thesecond or subsequent pattern overlaps or intersects with the firstpattern and glass is ablated from the glass substrate along the secondor subsequent pattern thereby forming at least one microstructure on theglass substrate.
 2. The method of claim 1 wherein the first patterncomprises a set of parallel lines and the second or subsequent patterncomprises a set of parallel lines and wherein the set of parallel linesof the first pattern are non-parallel with the set of parallel lines ofthe second or subsequent pattern such that the at least onemicrostructure formed on the glass substrate comprises a pattern ofmicrostructure pillars formed on the glass substrate at the intersticesbetween intersections of the set of parallel lines of the first patternand the set of parallel lines of the second or subsequent pattern. 3.The method of claim 2 wherein the set of parallel lines of the firstpattern is perpendicular to the set of parallel lines of the second orsubsequent pattern.
 4. The method of claim 2 wherein a pitch of the setof parallel lines of the first pattern and a pitch of set of parallellines of the second or subsequent pattern are selected based on thedesired dimensions of the microstructure pillars in the regular patternof microstructure pillars.
 5. The method of claim 1 wherein the firstpattern comprises a radial pattern centered on a center point and thesecond or subsequent pattern comprises a radial pattern centered on thecenter point overlapping the first pattern such that the at least onemicrostructure is a circular microstructure pillar or a circularmicrostructure cavity centered on the center point.
 6. The method ofclaim 1 wherein the beam of the laser source comprises a plurality oflaser pulses and the first pattern comprises a first plurality of laserpulses wherein a spot area of each laser pulse in the first plurality oflaser pulses overlaps a spot area of a preceding laser pulse, as spotarea of a subsequent laser pulse or both; and wherein the second orsubsequent pattern comprises a second or subsequent plurality of laserpulses wherein a spot area of each laser pulse in the second orsubsequent pattern of laser pulses overlaps a spot area of a precedinglaser pulse, a spot area of a subsequent laser pulse or both.
 7. Themethod of claim 6 wherein the first pattern comprises a linear patternof overlapping spot areas and the second or subsequent pattern comprisesa linear pattern of overlapping spot areas substantially parallel withand overlapping the first pattern such that the at least onemicrostructure formed on the glass substrate is a plurality of taperedmicrostructure cavities wherein each tapered microstructure cavity inthe plurality of tapered microstructure cavities has an opening having adiameter less than a diameter of a spot area of a laser pulse in thefirst pattern, a spot area of a laser pulse in a second pattern or both.8. The method of claim 6 wherein the first pattern comprises a set ofparallel lines with each line in the set of parallel lines comprising arow of overlapping spot areas and the second or subsequent patterncomprises a set of parallel lines with each line in the set of parallellines comprising a row of overlapping spot areas and wherein the set ofparallel lines of the first pattern are non-parallel with the set ofparallel lines of the second or subsequent pattern such that the atleast one microstructure formed on the glass substrate comprises aregular pattern of microstructure pillars formed on the glass substrateat the interstices between intersections of the set of parallel lines ofthe first pattern and the set of parallel lines of the second orsubsequent pattern.
 9. The method of claim 8 wherein the set of parallellines of the first pattern is perpendicular to the set of parallel linesof the second or subsequent pattern.
 10. The method of claim 8 wherein apitch of the set of parallel lines of the first pattern and a pitch ofset of parallel lines of the second or subsequent pattern are selectedbased on the desired dimensions of the microstructure pillars in theregular pattern of microstructure pillars.
 11. The method of claim 6wherein the first pattern comprises a radial pattern of overlapping spotareas centered on a center point such that a center of each spot area inthe first radial pattern is equidistant from the center point and thesecond or subsequent pattern comprises a radial pattern of overlappingspot areas centered on the center point such that a center of each spotarea in the second or subsequent radial pattern is equidistant from thecenter point and wherein the second or subsequent pattern isrotationally offset from the first pattern such that each spot area inthe at least one second pattern is non-concentric with the spot areas inthe first pattern thereby forming a circular microstructure pillar or acircular microstructure cavity on the glass substrate centered on thecenter point.
 12. The method of claim 11 wherein a radius of the firstradial pattern and a radius of the second or subsequent radial patternare selected such that the microstructure is a circular microstructurepillar.
 13. The method of claim 11 wherein a radius of the first radialpattern and a radius of the second or subsequent radial pattern areselected such that the microstructure is a circular microstructurecavity.
 14. The method of claim 11 wherein the second or subsequentradial pattern is offset from the first radial pattern such that eachspot area of each laser pulse in the second or subsequent radial patternis non-concentric with a spot area of a laser pulse in the first radialpattern.
 15. The method of claim 1 wherein the beam of the laser sourceis directed towards the surface of the glass substrate using a lasersystem comprising the laser source, a beam steering mechanism and a lenssystem wherein the beam from the laser source is directed into the beamsteering mechanism which redirects the beam towards the surface of theglass substrate and into the lens system which focuses the beam on thesurface of the glass substrate and wherein the beam steering mechanismis used in conjunction with the lens system to position the laser pulseson the surface of the glass substrate.
 16. The method of claim 15wherein the beam steering mechanism comprises at least one galvanometermirror for redirecting the beam, the laser source comprises a CO₂ laserand the lens system comprises an F-theta lens.
 17. A method for formingmicrostructure cavities in a glass substrate, the method comprising:directing a first laser pulse onto the glass substrate thereby forming afirst microstructure cavity having a tapered configuration in the glasssubstrate wherein the first laser pulse has a first spot area on thesurface of the substrate; directing a second laser pulse having a secondspot area onto the glass substrate such that the second spot areaoverlaps the first spot area thereby forming a second microstructurecavity having a tapered configuration in the glass substrate wherein thesecond spot area is substantially the same as the first spot area on thesurface of the substrate and wherein overlapping the second spot areaover the first spot area ablates a portion of a sidewall disposedbetween the first microstructure cavity and the second microstructurecavity such that, after a portion of the sidewall is ablated, a diameterof an opening of the first cavity and a diameter of an opening of thesecond cavity are less than a diameter of the first spot area and/or adiameter of the second spot area.
 18. The method of claim 17 furthercomprising directing a plurality of laser pulses onto the surface of theglass substrate such that a spot area of each laser pulse in theplurality of laser pulses overlaps the spot area of a preceding laserpulse, a subsequent laser pulse or both and wherein at least one spotarea of at least one laser pulse overlaps at least one of the first spotarea or the second spot area thereby forming a plurality ofmicrostructure cavities having tapered configurations in the glasssubstrate and wherein the spot area of each laser pulse in the pluralityof laser pulses is substantially the same as the first spot area, thesecond spot area or both on the surface of the substrate and whereineach microstructure cavity in the plurality of microstructure cavitieshas an opening having a diameter less than the diameter of the firstspot area.
 19. The method of claim 18 wherein the plurality of laserpulses are directed onto the glass substrate in parallel rows such thatthe spot area of each laser pulse in a row of laser pulses overlaps withthe spot area of a preceding laser pulse in the row, a subsequent laserpulse in the row or both.
 20. The method of claim 19 wherein adjacentparallel rows of laser pulses overlap and wherein the adjacent parallelrows of laser pulses are offset such that a center of each laser pulsein one parallel row is disposed between the centers of two consecutivelaser pulses in an adjacent parallel row thereby forming a honeycombpattern of microstructure cavities on the glass substrate.